<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
	<title>圆角</title>
	<style type="text/css">
	#main{
		width: 100px;
		height: 100px;
		background: red;
		border-radius: 5px;
	}
	</style>
</head>
<body>
<div id="main"></div>
</body>
</html>